High-temperature-resistant modified polyvinyl alcohol and preparation method and application thereof

Abstract

The application provides a high-temperature-resistant modified polyvinyl alcohol and a preparation method and application thereof. The high-temperature-resistant modified polyvinyl alcohol is obtained by modifying polyvinyl alcohol by a modifier under alkaline conditions. The application uses chloroacetic acid, 2-chloroethyl-trimethylammonium chloride, 2-bromoethyl-trimethylammonium bromide, 3-chloro-2-hydroxypropyl-trimethylammonium chloride and a combination thereof as the modifier. After modification, the solubility of the matrix is improved. The introduction of carboxyl, ammonium and other ionized groups increases the repulsion between the main chains, so that the main chains are more fully stretched, more easily crosslinked to form a network structure, the stability of the fluid loss additive molecules is enhanced, the fluid loss additive molecules cannot be decomposed or hydrolyzed under high-temperature conditions, the volume and steric hindrance of the fluid loss additive molecules can be increased, and the high-temperature resistance of the fluid loss additive molecules is improved. Meanwhile, the introduction of large polar groups such as carboxyl and ammonium also enhances the adsorption of the high-temperature-resistant modified polyvinyl alcohol to the surface of particles in the cement slurry, which is conducive to improving the fluid loss effect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas field cementing, and particularly relates to a high-temperature-resistant modified polyvinyl alcohol and a preparation method and application thereof. BACKGROUND

[0002] During the development of oil and gas fields, drilling operations are generally performed first, and then cementing operations are performed. Drilling operations generally use drilling fluid, and cementing operations generally use cement slurry. The cementing operation mainly injects cement slurry into the annulus between the well wall and the casing, and allows it to return to a certain height, so that the cement slurry is solidified to cement the well wall and the casing, thereby playing a role in cementing. However, during the pumping process, the cement slurry will lose water when passing through permeable formations under the action of pump pressure and formation pressure. If the water loss is too much, it will affect the performance of the cement slurry, and in severe cases, it will cause cementing plugging and cause safety accidents. Therefore, a water loss reducer is generally added when preparing the cement slurry to reduce the water loss of the cement slurry and avoid affecting the performance of the cement slurry.

[0003] Polyvinyl alcohol is commonly used in oil fields as a cement slurry loss reducer, and is suitable for use at 50-85℃. When the temperature is further increased, the molecular chain will be curled, the entanglement between molecules will be reduced, the network structure will be weakened until it is disintegrated, and the water loss reduction effect will be significantly reduced. As the oil field development deepens, the well depth gradually increases, and the requirement for the temperature resistance of the water loss reducer gradually increases. Therefore, polyvinyl alcohol cannot be used in environments above 85℃. Although other polymer water loss reducers can be used, the cost is significantly increased, and the environmental protection performance is reduced.

[0004] In addition to the above, commonly used polymer water reducers include AMPS (2-Acrylamido-2-Methyl Propanesulfonic Acid), acrylamide, N,N-dimethyl acrylamide, acrylic acid, methacrylic acid, maleic anhydride, or itaconic acid. However, when the cement slurry is injected into a deep formation with a high formation temperature, the amide groups in the water loss reducers used in the related art, such as AMPS, acrylamide, and N,N-dimethyl acrylamide, are prone to decomposition or hydrolysis, and the molecular chain is prone to stretching or breaking, resulting in shear thinning of the cement slurry prepared using the water loss reducer, a large change in the rheological properties of the cement slurry, low displacement efficiency of the cement slurry for displacing drilling fluid, and poor cementing quality. SUMMARY

[0005] The purpose of the present application is to provide a high-temperature-resistant modified polyvinyl alcohol that overcomes the above technical problems in the prior art.

[0006] Another object of the present application is to provide a preparation method of the high-temperature-resistant modified polyvinyl alcohol, which increases water-soluble groups on the polyvinyl alcohol chain and improves the solubility of the matrix by modifying the polyvinyl alcohol under alkaline conditions.

[0007] Another object of the present application is to provide an application of the high-temperature-resistant modified polyvinyl alcohol, which has excellent fluid loss control performance in cement slurry and good well cementing effect.

[0008] To achieve the above objects, the present application provides the technical solutions as follows.

[0009] The high-temperature-resistant modified polyvinyl alcohol is obtained by modifying the polyvinyl alcohol with a modifier under alkaline conditions, and the modifier is an organic chloride or an organic bromide.

[0010] The modifier is one or a combination of several of chloroacetic acid, 2-chloroethyl-trimethylammonium chloride, 2-bromoethyl-trimethylammonium bromide and 3-chloro-2-hydroxypropyl-trimethylammonium chloride.

[0011] The amount of the modifier is 0.1-2% of the mass of the polyvinyl alcohol.

[0012] The polyvinyl alcohol is polyvinyl alcohol 1788, polyvinyl alcohol 1799 or polyvinyl alcohol 2099 with a mesh size of 40-200.

[0013] Step 1) dispersing the polyvinyl alcohol in a solvent in a container, and adding the modifier in the formula amount while stirring until uniform;

[0014] Step 2) stirring and heating the reactants in the container at 60-100℃ for 1-6 hours, adding an alkali solution to the reaction system to adjust the pH value to 7-8 during the reaction, and cooling to room temperature after the reaction is completed;

[0015] Step 3) filtering and drying for 1-12 hours to obtain the high-temperature-resistant modified polyvinyl alcohol.

[0016] The mass of the solvent is 5-50 times of the mass of the polyvinyl alcohol, the solvent is an alcohol-water mixture, and the volume ratio of alcohol to water in the alcohol-water mixture is 100:1-10.

[0017] The alcohol is industrial-grade or above-purity methanol, ethanol, propanol, isopropanol and a combination thereof, and the water is industrial-grade or above-purity tap water, deionized water, distilled water and a combination thereof.

[0018] The alkali solution is an aqueous solution of industrial-grade or above-purity sodium hydroxide, potassium hydroxide and a combination thereof.

[0019] The application of a high-temperature-resistant modified polyvinyl alcohol in cement slurry, the high-temperature-resistant modified polyvinyl alcohol is used as a fluid loss additive in the cement slurry, and the amount of the high-temperature-resistant modified polyvinyl alcohol accounts for 0.3-3% of the mass percentage of the cement slurry.

[0020] The application has the following advantages:

[0021] The high-temperature-resistant modified polyvinyl alcohol provided by the application is modified by using chloroacetic acid, 2-chloroethyl-trimethylammonium chloride, 2-bromoethyl-trimethylammonium bromide, 3-chloro-2-hydroxypropyl-trimethylammonium chloride and combinations thereof as a modifier, so that the water-soluble groups on the polyvinyl alcohol chain are increased, the solubility of the matrix is improved, the introduction of the carboxyl group and the ammonium group increases the repulsion between the main chains, so that the main chains are more fully stretched, and the introduction of the carboxyl group and the ammonium group also enhances the adsorption of the high-temperature-resistant modified polyvinyl alcohol to the surface of particles in the cement slurry, which is beneficial to improving the fluid loss effect.

[0022] The high-temperature-resistant polyvinyl alcohol with a mass percentage of 0.3-3% is added into the oilfield cementing water-based cement slurry, and the fluid loss amount is measured at 90-120 DEG C, and the fluid loss amount is reduced by 30-80% compared with the unmodified polyvinyl alcohol. Due to the introduction of the carboxyl group and the ammonium group, the main chain of the modified polyvinyl alcohol is more fully stretched, and is more easily crosslinked to form a network structure, so that the stability of the fluid loss additive molecules is enhanced, and the fluid loss additive molecules will not be decomposed or hydrolyzed under high-temperature conditions, the volume and the steric hindrance of the fluid loss additive molecules can be increased, and the high-temperature resistance of the fluid loss additive molecules can be improved, so that the cement slurry prepared by using the fluid loss additive can maintain the rheological property basically unchanged under the premise of ensuring the fluid loss control performance under high-temperature conditions, so that the displacement efficiency of the cement slurry to the drilling fluid under high-temperature conditions can be improved, and the cementing quality can be improved.

[0023] The following will be further described in detail. DETAILED DESCRIPTION

[0024] The embodiments of the application will be described in conjunction with the specific embodiments described below, and other advantages and effects of the application can be easily understood by those skilled in the art from the content disclosed in the specification.

[0025] The exemplary embodiments of the application are introduced, however, the application can be implemented in many different forms, and is not limited to the embodiments described herein, and these embodiments are provided to thoroughly and completely disclose the application, and to fully convey the scope of the application to those skilled in the art. The terms expressed in the exemplary embodiments are not a limitation of the application.

[0026] The application provides a high-temperature-resistant modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol under alkaline conditions by using a modifier.

[0027] The modifier is one or several combinations of chloroacetic acid, 2-chloroethyl-trimethylammonium chloride, 2-bromoethyl-trimethylammonium bromide, 3-chloro-2-hydroxypropyl-trimethylammonium chloride.

[0028] The amount of the modifier is 0.1-2% of the mass of the polyvinyl alcohol.

[0029] The polyvinyl alcohol is polyvinyl alcohol 1788, polyvinyl alcohol 1799 or polyvinyl alcohol 2099 with a mesh of 40-200.

[0030] This embodiment provides a high-temperature resistant modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol with a modifier chloroacetic acid under alkaline conditions. The amount of chloroacetic acid added is 0.3% of the mass of the polyvinyl alcohol.

[0031] The preparation method comprises the following steps:

[0032] Firstly, polyvinyl alcohol powder is dispersed in 5 times of mass of solvent in a container, the polyvinyl alcohol powder is industrial-grade polyvinyl alcohol 1788 with a mesh of 40-80, and the solvent is an alcohol-water mixed solution with a ratio of 100:1, wherein the alcohol is industrial-grade methanol and the water is industrial-grade deionized water;

[0033] Secondly, the formula amount of industrial-grade chloroacetic acid is added to the container under stirring;

[0034] Thirdly, the reactants in the container are heated and stirred at 60°C for 6 hours, and during the reaction, an alkaline solution with a mass concentration of 1% is added to the reaction system to adjust the pH value to 7-8, and after the reaction is completed, the temperature is cooled to room temperature, wherein the alkali is industrial-grade sodium hydroxide;

[0035] Fourthly, filtration and drying at room temperature for 12 hours are performed to obtain the high-temperature resistant polyvinyl alcohol.

[0036] The reaction principle is as follows:

[0037]

[0038] In this embodiment, polyvinyl alcohol is modified by chloroacetic acid under alkaline conditions, which increases the water-soluble groups on the polyvinyl alcohol chain, improves the solubility of the matrix, increases the repulsion between the main chains due to the introduction of carboxyl groups, so that the main chains are more fully stretched, and the introduction of carboxyl groups also enhances the adsorption of the particles on the surface of the cement slurry, which is beneficial to improve the effect of reducing the filtration loss.

[0039] Example 2:

[0040] The embodiment provides a high-temperature-resistant modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol by a modifier 2-chloroethyl-trimethyl ammonium chloride under alkaline conditions. The 2-chloroethyl-trimethyl ammonium chloride is chemically pure, and the adding amount is 0.5% of the mass of the polyvinyl alcohol.

[0041] The preparation method comprises the following steps:

[0042] In the first step, polyvinyl alcohol powder is dispersed in 10 times of mass of a solvent in a container, the polyvinyl alcohol powder is chemically pure polyvinyl alcohol 1799 with a mesh of 80-100, and the solvent is an alcohol-water mixed solution with a proportion of 100:5, wherein the alcohol is chemically pure ethanol, and the water is distilled water.

[0043] In the second step, the formula amount of 2-chloroethyl-trimethyl ammonium chloride is added to the container under stirring.

[0044] In the third step, the reactants in the container are heated and stirred at 70 DEG C for 5 hours, a 2% mass concentration of an alkali solution is added to the reaction system during the reaction to adjust the pH value to 7-8, and the reaction is cooled to room temperature after the reaction is completed, wherein the alkali used is chemically pure potassium hydroxide.

[0045] In the fourth step, filtration and drying at 30 DEG C for 12 hours are performed, and the high-temperature-resistant polyvinyl alcohol is obtained.

[0046] The reaction principle is as follows:

[0047]

[0048] The embodiment modifies polyvinyl alcohol by using 2-chloroethyl-trimethyl ammonium chloride under alkaline conditions, increases water-soluble groups on the polyvinyl alcohol chain after modification, improves the solubility of the matrix, increases the repulsion between the main chains due to the introduction of the ammonium group, so that the main chain is more fully stretched, the molecules are easily entangled to form a network structure, and the introduction of the ammonium group also enhances the adsorption of the particles on the surface of the cement slurry, which is beneficial to improving the fluid loss effect.

[0049] Embodiment 3:

[0050] The embodiment provides a high-temperature-resistant modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol by a modifier 2-chloroethyl-trimethyl ammonium chloride under alkaline conditions. The 2-chloroethyl-trimethyl ammonium chloride is chemically pure, and the adding amount is 0.5% of the mass of the polyvinyl alcohol.

[0051] The preparation method comprises the following steps:

[0052] The first step is to disperse polyvinyl alcohol powder in 20 times the mass of solvent in a container, the polyvinyl alcohol powder is analytical pure 120-200 mesh polyvinyl alcohol 2099, and the solvent is an alcohol-water mixed solution with a proportion of 100:10, wherein the alcohol is analytical pure propanol and the water is distilled water;

[0053] The second step is to add the formula amount of 2-bromoethyl-trimethylammonium bromide to the container under stirring;

[0054] The third step is to stir and heat the reactants in the container at 90°C for 2 hours, during the reaction, a 5% alkali solution by mass concentration is added to the reaction system to adjust the pH value to 7-8, and after the reaction is completed, the temperature is cooled to room temperature, and the alkali is analytical pure sodium hydroxide;

[0055] The fourth step is to filter and dry at 45°C for 8 hours to obtain the high-temperature-resistant polyvinyl alcohol.

[0056] The reaction principle is the same as that of Example 2.

[0057] The high-temperature-resistant modified polyvinyl alcohol obtained after modification has excellent water loss control performance. Moreover, as the temperature rises, the molecular form of the fluid loss additive does not change, and the viscosity remains basically unchanged. Therefore, the cement slurry prepared with the fluid loss additive can maintain its rheological data basically unchanged under high temperature conditions on the premise of ensuring its water loss control performance, thereby improving the displacement efficiency of the cement slurry to the drilling fluid and improving the cementing quality.

[0058] Example 4:

[0059] The present embodiment provides a high-temperature-resistant modified polyvinyl alcohol, which is obtained by modifying polyvinyl alcohol with a modifier 3-chloro-2-hydroxypropyl-trimethylammonium chloride under alkaline conditions. The 3-chloro-2-hydroxypropyl-trimethylammonium chloride is of industrial grade, and the addition amount is 1.5% of the mass of the polyvinyl alcohol.

[0060] The preparation method comprises the following steps:

[0061] The first step is to disperse polyvinyl alcohol powder in 30 times the mass of solvent in a container, the polyvinyl alcohol powder is industrial grade 140-200 mesh polyvinyl alcohol 1788, and the solvent is an alcohol-water mixed solution with a proportion of 100:8, wherein the alcohol is industrial grade isopropanol and the water is industrial grade tap water;

[0062] The second step is to add the formula amount of 3-chloro-2-hydroxypropyl-trimethylammonium chloride to the container under stirring;

[0063] The third step is to stir and heat the reactants in the container at 80°C for 3 hours, during the reaction, a 10% alkali solution by mass concentration is added to the reaction system to adjust the pH value to 7-8, and after the reaction is completed, the temperature is cooled to room temperature. The alkali used is industrial grade potassium hydroxide.

[0064] Fourth step, filtration, 60℃ under drying 3 hours, namely the high temperature resistant polyvinyl alcohol is obtained.

[0065] Reaction principle common example 2.

[0066] By modifying polyvinyl alcohol, introducing carboxyl or ammonium group, the main chain is more fully stretched, intermolecular easy winding to form a network structure, enhance the stability of the molecule, avoid the cement paste dilution, affect the rheological properties of cement paste.

[0067] Example 5:

[0068] The embodiment provides a kind of high temperature resistant modified polyvinyl alcohol, in alkaline conditions, by modifying agent chloroacetic acid and 3-chloro-2-hydroxypropyl-trimethylammonium chloride to polyvinyl alcohol after modification is obtained.Therein, chloroacetic acid and 3-chloro-2-hydroxypropyl-trimethylammonium chloride are all industrial grade, and the amount of addition is 2% of the mass of polyvinyl alcohol, and the mass ratio of the two is 1:2.

[0069] Preparation method includes the following steps:

[0070] First step, polyvinyl alcohol powder is dispersed in 20 times mass of solvent in container, polyvinyl alcohol powder is industrial grade polyvinyl alcohol 2099, and the solvent is alcohol-water mixed solution with the proportion of 100:5, wherein alcohol is industrial grade ethanol, and water is industrial grade deionized water;

[0071] Second step, add the amount of modification agent into the container under stirring;

[0072] Third step, the reactant in container is heated and stirred at 75 DEG C for 4 hours, and during the reaction, 8% alkali solution is added to the reaction system, and the pH value is kept at 7-8, after the reaction, it is cooled to room temperature;Wherein, the alkali used is industrial grade sodium hydroxide;

[0073] Fourth step, filtration, 60℃ under drying 2 hours, namely the high temperature resistant polyvinyl alcohol is obtained.

[0074] Reaction principle common example 1 and example 2.

[0075] Example 6:

[0076] The embodiment provides a kind of high temperature resistant modified polyvinyl alcohol, in alkaline conditions, by modifying agent to polyvinyl alcohol after modification is obtained.Therein, the modifying agent is the combination of chloroacetic acid, 2-chloroethyl-trimethylammonium chloride and 3-chloro-2-hydroxypropyl-trimethylammonium chloride, and chloroacetic acid, 2-chloroethyl-trimethylammonium chloride and 3-chloro-2-hydroxypropyl-trimethylammonium chloride are all industrial grade, and the amount of addition is 1% of the mass of polyvinyl alcohol, and the mass ratio of the three is 2:1:3.

[0077] The preparation method comprises the following steps:

[0078] In the first step, polyvinyl alcohol powder is dispersed in 15 times the mass of solvent in a container, the polyvinyl alcohol powder is analytical pure 80-100 mesh polyvinyl alcohol 1799, and the solvent is an alcohol-water mixed solution with a proportion of 100:5, wherein the alcohol is analytical pure propanol and the water is industrial grade distilled water;

[0079] In the second step, the modified agent is added to the container under stirring in an amount according to the formula;

[0080] In the third step, the reactants in the container are heated and stirred at 85 DEG C for 3 hours, an alkali solution with a mass concentration of 7.5% is added to the reaction system during the reaction to adjust the pH value to 7-8, and the reaction is cooled to room temperature after completion; wherein the alkali used is industrial grade potassium hydroxide;

[0081] In the fourth step, filtration and drying at 50 DEG C for 4 hours are performed to obtain the high-temperature-resistant polyvinyl alcohol.

[0082] The reaction principle is the same as that in Embodiment 1 and Embodiment 2.

[0083] The high-temperature-resistant modified polyvinyl alcohol can improve the high-temperature resistance of the fluid loss agent molecules, so that the cement slurry prepared by using the fluid loss agent can maintain the rheological property basically unchanged under the premise of ensuring the fluid loss control performance under high temperature, thereby improving the displacement efficiency of the cement slurry for displacing the drilling fluid under high temperature and improving the cementing quality.

[0084] Embodiment 7:

[0085] The embodiment provides an application of the high-temperature-resistant modified polyvinyl alcohol in a cement slurry, wherein the high-temperature-resistant modified polyvinyl alcohol is used as a fluid loss agent in the cement slurry, and the amount of the high-temperature-resistant modified polyvinyl alcohol accounts for 0.3-3% of the mass percentage of the cement slurry.

[0086] The cement slurries prepared by using the fluid loss agents with different mass fractions in Embodiments 1-6 are tested for fluid loss performance under 90-120 DEG C, and the test method is performed according to "SY / T 5504.2-2013 Oil Well Cement Additive Evaluation Method Part 2: Fluid Loss Agent", and the test results are shown in Table 1. The polyvinyl alcohol before modification is also tested for fluid loss performance according to the above test method, and the results are shown in Table 2.

[0087] Table 1 Fluid loss amount of the cement slurry prepared by using the fluid loss agents in Embodiments 1-6

[0088]

[0089] Table 2 Fluid loss amount of the unmodified polyvinyl alcohol under different amounts and temperatures

[0090]

[0091] From the test results of Table 1, it can be seen that the modified polyvinyl alcohol prepared cement slurry, with the increase of the amount of the fluid loss agent

[0092] the amount of the fluid loss agent, the amount of the fluid loss of the cement slurry gradually decreases. At 100℃, when the amount of the modified polyvinyl alcohol is 1.2%, the amount of the fluid loss of the cement slurry can be controlled at 35ml, which shows that the modified polyvinyl alcohol has excellent fluid loss control performance.

[0093] From the comparison of Table 1 and Table 2, it can be seen that the amount of the fluid loss of the modified polyvinyl alcohol at 90-120℃ is reduced by 30-80% compared with the unmodified polyvinyl alcohol.

[0094] The above examples are only illustrative of the present application and do not constitute a limitation on the protection scope of the present application, and any design identical or similar to the present application falls within the protection scope of the present application.

Claims

1. A high temperature resistant modified polyvinyl alcohol, characterized in that: The modified polyvinyl alcohol is obtained by modifying polyvinyl alcohol under alkaline conditions by using a modifier to increase water-soluble groups on the polyvinyl alcohol chain, wherein the modifier is an organic chloride or an organic bromide; The modifier is a combination of one or more of chloroacetic acid, 2-chloroethyl-trimethylammonium chloride, 2-bromoethyl-trimethylammonium bromide, and 3-chloro-2-hydroxypropyl-trimethylammonium chloride; The high-temperature-resistant modified polyvinyl alcohol is prepared by the following steps: Step 1) dispersing polyvinyl alcohol in a solvent in a container, stirring uniformly, and then adding the modifier while stirring; Step 2) stirring and heating the reactants in the container at 60-100°C for 1-6 hours, adding an alkali solution to the reaction system during the reaction to adjust the pH value to 7-8, and cooling to room temperature after the reaction is completed; Step 3) filtering and drying for 1-12 hours to obtain the high-temperature-resistant modified polyvinyl alcohol; The high-temperature-resistant modified polyvinyl alcohol is used as a fluid loss additive in cement slurry.

2. The high temperature resistant modified polyvinyl alcohol according to claim 1, characterized in that: The amount of the modifier is 0.1-2% of the mass of the polyvinyl alcohol.

3. A high temperature resistant modified polyvinyl alcohol according to any one of claims 1-2, characterized in that: The polyvinyl alcohol is polyvinyl alcohol 1788, polyvinyl alcohol 1799, or polyvinyl alcohol 2099 with a mesh number of 40-200.

4. A process for the preparation of a high temperature resistant modified polyvinyl alcohol according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step 1) dispersing polyvinyl alcohol in a solvent in a container, stirring uniformly, and then adding the modifier in the formula amount while stirring; Step 2) stirring and heating the reactants in the container at 60-100°C for 1-6 hours, adding an alkali solution to the reaction system during the reaction to adjust the pH value to 7-8, and cooling to room temperature after the reaction is completed; Step 3) filtering and drying for 1-12 hours to obtain the high-temperature-resistant modified polyvinyl alcohol.

5. The method for preparing high-temperature resistant modified polyvinyl alcohol according to claim 4, characterized in that: The mass of the solvent is 5-50 times the mass of the polyvinyl alcohol, the solvent is an alcohol-water mixture, and the volume ratio of alcohol to water in the alcohol-water mixture is 100:1-10.

6. The method for preparing high-temperature resistant modified polyvinyl alcohol according to claim 5, characterized in that: The alcohol is methanol, ethanol, propanol, isopropanol, or a combination thereof, all of which are of industrial grade or above in purity; and the water is tap water, deionized water, or distilled water, or a combination thereof, all of which are of industrial grade or above in purity.

7. The method for preparing high-temperature resistant modified polyvinyl alcohol according to claim 5, characterized in that: The alkali solution is an aqueous solution of sodium hydroxide or potassium hydroxide, or a combination thereof, all of which are of industrial grade or above in purity.

8. Use of a high temperature resistant modified polyvinyl alcohol according to any one of claims 1-2 in cement slurries, characterized in that: The high-temperature-resistant modified polyvinyl alcohol is used as a fluid loss additive in cement slurry, and the amount is 0.3-3% of the mass percentage of the cement slurry.

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